79255-01-9Relevant articles and documents
Iminium Salts from α-Amino Acid Decarbonylation. Application to the Synthesis of Octahydroindoloquinolizines
Johansen, Jon E.,Christie, Bradley D.,Rapoport, Henry
, p. 4914 - 4920 (2007/10/02)
Iminium salts, formed regiospecifically by the decarbonylation of tertiary α-amino acids, have been applied to the synthesis of substituted tetrahydro-β-carbolines.In this manner the octahydroindoloquinolizines 5-8 were prepared.Several useful methods for the synthesis of the requisite tertiary pipecolic acids 1-4 were developed.These include alkylation of secondary α-amino esters with tryptophyl bromide and alkylation of tryptophan methyl ester with α,ω-dibromo esters.Following deprotection, the resulting tertiary α-amino acids were heated in phenylphosphonic dichloride to give the cyclized products in good yield.The presence of other substituents α or β to the basic nitrogen induces stereoselectivity in the ring closure.When this substituent is an α-carboxylic acid, it can be replaced by hydrogen through decarbonaylation followed by reduction of the resulting iminium salt.
